Parallel constructions with two different guides are already known, whereby one of the two guides is generally made narrower and incapable of accepting lateral forces (U.S. Pat. No. 3,148,742, cited in German Utility Model 71-15,570). A similar function is provided in the parallel construction according to Swiss Pat. No. 525,476, wherein two cross-brace joints are provided above and one below. In such asymmetric guides, however, only one guide form can be disposed optimally relative to accepting forces in various directions, while the second guide can fulfill its function only partially. Consequently, the accuracy of the parallel construction suffers. In addition, two different parts must be manufactured, stored and (in the event of repair) brought along, which should be avoided for space and cost reasons.
Hence, parallel constructions with two identical guides have been developed, whereby the articulations form the corners of a rectangle. A design of this kind has been proposed, for example, for a electromagnetically compensating, beamless force-measuring or weighing device in U.S. Pat. No. 4,062,416. Such parallel constructions are known, with two identical guides, from U.S. Pat. No. 3,877,532 or German Utility Model 71-15,570. The articulations are generally formed by thin leaf springs or appropriate thin places on the arms.
In addition, an E-shaped guide geometry is known from U.S. Pat. No. 3,191,702, wherein the ends of the two outer tabs of the guides are permanently mounted, while the movable, rigid connecting element is mounted on the end of the middle tab of the guides. Hence, the entire guide is made in the form of a spring. The two guides of the parallel construction are again mounted vertically one above the other.
Hence, the guides must be screwed from above or below to a system support, in other words to an additional element, which can only then be connected (for example by screwing), to the housing, especially the bottom plate of the balance. Admittedly, U.S. Pat. No. 3,191,702 indicates a direct support of the parallel construction on a part of the housing; in this case, however, the fastening screws are difficult to reach; moreover, screwing points must be used which are less stable because they are projecting.